1 #include <iostream>
 2 using namespace std;
 3 void cheng(int a,int b){
 4     if(a<=9){
 5         if(b<=a){
 6             cout<<a<<"x"<<b<<"="<<a*b<<" ";
 7             cheng(a,b+1);
 8         }
 9         cout<<endl;
10     }
11     cheng(a+1,1);
12 }
13 int main(int argc, char** argv) {
14     cheng(1,1);
15     return 0;
16 }